[Pacemaker] how to use dlm and clvm with pacemaker ?

[Andrew Beekhof]

On Sun, Sep 16, 2012 at 2:23 AM, denis bonnenfant
<denis.bonnenfant at diderot.org> wrote:
> Hello,
>
> I'm currently running in production a 3-nodes corosync/pacemaker/drbd/clvm
> xen virtualisation cluster, based on debian wheezy.
>
> Two nodes are running drbd inactive/active setup, with clustered VGs
> (/dev/xen-data) on top of drbd disk for local domUs , and ISCSI target  LV (
> /dev/xen-data/iscsi-target)  for the third node with a virtual ip for
> failover.
>
> On both nodes another clustered VG is running on the iscsi initiator
> (/dev/xen-iscsi).
>
> LV-based DomUs can live migrate between the 2 drbd nodes if they are on drbd
> VG,  or between all the nodes if they are on the iscsi VG.
>
> This setup works quite well, except for one point :  sometimes, when a node
> falls down, dlm is locking down all the lvm layer, causing all nodes to
> fence each other. The problem is not related with the stacked lvm setup, as
> it occurs even when no iscsi resources are started.
>
> This problem is well known, and new versions of cman totally remove
> dlm_controld.pcmk. But then documentations are quite confusing :
>
> -
> http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Clusters_from_Scratch/apcs02.html
> advises to run cman from init scripts with a configured /etc/cluster.conf,
> and then start pacemaker  from init,
> -
> http://www.clusterlabs.org/doc/en-US/Pacemaker/1.1/html/Clusters_from_Scratch/apcs02s02.html
> advises to run corosync with a cman plugin, but don't say how to start
> pacemaker?

Also with the init script.  They are really talking about the same
thing... cman is "only" a corosync plugin.
Sorry for the confusion.

> - some other advise to modify controld RA to use directly new dlm_controld
> (how ? symlink dlm_controld.pcmk ?)
>
> Before bringing my cluster down, I want to be sure about the best path for
> upgrading.
>
>
> As I'm running redundant rings in corosync, adding cman stuff in my
> corosync.conf  seems for me the simplest,

I believe its not hard with cluster.conf too, I just haven't done it personally.

> but in this case, do I still need
> to configure controld and clvm in crm, or are they completely managed by the
> cman plugin ? do I need to start pacemaker from corosync config too ?
>
> http://theclusterguy.clusterlabs.org/post/907043024/introducing-the-pacemaker-master-control-process-for
> seems to suggest that in my case, with dlm and clvm involved, option 3 with
> cluster.conf is the best approach. But how pacemaker is started in this
> case,  from init  after cman ?

Correct

> Do I need up-to date version of cman, or is debian wheezy  version (3.0.12)
> ok ?

I don't think its been changing much.  Whatever you have should be fine.

> Do I need up-to date version of pacemaker, or is debian wheezy version
> (1.1.7) ?, recompiled with --with-cman ?

If you run pacemakerd --features, it should indicate whether cman
support was built in.

>
> Regards,
>
> Denis
>
> _______________________________________________
> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
>
> Project Home: http://www.clusterlabs.org
> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> Bugs: http://bugs.clusterlabs.org